A complex carbohydrate in a cell plays an important role in information transfer, identification among cells and recognition of a virus, cancer cell, blood type and others. Clarification of oligosaccharide functions is ranked as one of the major tasks that come after the study of genome. An oligonucleic acid and peptide synthesis method have been already established and automated. Oligosaccharide synthesis, however, has many problems yet to be solved.
In an effort to clarify the functions of oligosaccharide, establishment of oligosaccharide synthesis method and creation of an effective synthesizer have been long awaited. At present, the following three methods of oligosaccharide synthesis are practiced:                (1) Chemical synthesis        (2) Genetically recombinant cell or fermentation by microorganism        (3) Synthesis by glycosyltransferase        
The method (1) is characterized by complicated steps of synthesis, since sequential synthesis of target oligosaccharides is performed while protecting the OH group other than the OH group for chemical bondage. The method (2) is characterized in that, although a great numbers of target oligosaccharides can be obtained, subsequent steps of purification are complicated. The method (3) was developed to solve the problems encountered in the complicated steps in methods (1) and (2). It is disclosed in the Japanese Patent Laid-Open Publication No. 11-42096 (1999), for example. The method (3) is based on synthesis by selective glycosyltransferase, and does not require protection of the OH-group, as in method (1). Further, there is not much quantity of by-products, and purification process subsequent to synthesis is easy.
A oligosaccharide synthesizer is disclosed in the Japanese Patent Laid-Open No. 05-500905 (1993).
When an actual apparatus is used to carry out the synthesis of a oligosaccharide based on the aforementioned method (3) a batch system is used at present, wherein separation and purification of products are carried out for each step in the reaction of a plurality of sugars performed one after another. The next reaction is carried out after that. Manpower is essential to complete the entire processing, according to this method.
In the apparatus disclosed in the aforementioned Japanese Patent Laid-Open No. 05-500905, according to the order of sugars to be reacted, reaction columns and separation/purification means must be connected on a continuous basis.
To put it another way, even if the same sugars are reacted, the same number of reaction columns and separation/purification means as that of sugars are required. This requires a large-scale system of apparatuses.
Further, glycosyltransferase needed for reaction is generally very expensive. Any arrangement for permitting repeated use of glycosyltransferase is not taken into account.